Method of alloying calcium with magnesium



Patented Apr. 1, 1941 r METHOD OF ALLOYING CALCl UM wrrn MAGNESIUMCharles E. Nelson, Midland, Mich, assignor to The Dow Chemical Company,Midland, Mich" a corporation of Michigan No Drawing. Application October25, 1939,

Serial No. 301,170

2 Claims.

The invention relates to a method of alloying calcium with magnesium ormagnesium base alloys.

It is a well known fact that, if an attempt is made to alloy a smallamount of calcium with magnesium to produce magnesium base alloys, it isexceedingly difficult, if not impossible, to predict the amount of'calcium that will be required in order that an alloy of the desiredcomposition will be produced. This is due to the fact that the meltingpoint of the calcium is so high, that it tends to burn or oxidize beforeit can be properly alloyed, even when protective means are employed incarrying out the operation. For this reason, an unpredictable or unknownamount of calcium is lost during the alloying operation, thus resultingin an alloy of unknown calcium content. A further difliculty isencountered when attempting to alloy calcium with magnesium due to thefact that it is difiicult to keep the surface of the calcium metal cleanenough to alloywith magnesium. For example, since calcium metaldeteriorates rapidly in storage due to the formation of an oxide orhydroxide coating on its surface. it is usually necessary to thoroughlyclean the surface of the metal by sand blasting every time it is used.This is not only a time-consuming operation, but it also results in lossof a very substantial amount of metal due to oxidation if the calcium 1is stored for any length of time.

It is, therefore, an object of the invention to provide a source ofcalcium having a low melting point so that it may be suitably alloyedwith magnesium base alloys without burning of the 1 a definite amount ofcalcium to be readily added to magnesium base alloys and at the sametime a source of calcium is provided that may be stored over longperiods of time without loss of metal due to surface oxidation. Further,the surface of the calcium alloys containing a small pertion ordeterioration had taken place.

centage of magnesium resist corrosion so efiectively that it is usuallyunnecessary to subject the metal to a cleaning operation before alloyingit with magnesium base alloys.

The amount of magnesium to add to form a calcium base alloy having theabove characteristics is from 18 to 23 per cent and preferably betweenabout 20 to 22 per cent. Alloys of this composition have a melting pointof from 430 to 470 C. as compared to 810 C. for pure calcium and thusserve as a source of calcium that may be readily alloyed with magnesiumwithout burning of the calcium. As aforementioned, these calcium alloyspossess highly desirable surface corrosion characteristics.

As an illustration of the superior surface oxidation characteristics ofthe calcium rich alloys as compared to calcium metal, a calcium alloywas made up containing about 20 per cent magnesium and stored for over ayear. After this time, it was observed that no appreciable oxida- On theother hand, pure calcium stored in a similar manner deteriorated rapidlyfrom day to day so that a block of the metal completely disintegrated inmuch less than a years time.

These alloys containing from 18 to 23 per cent magnesium are best madeby adding the requisite amount of clean pure calcium to molten magnesiumwith stirring while protecting the surface of the molten metals withnatural gas. It is preferable to add the calcium to the moltenmagnesium, since the temperature required is much lower than when themetals are alloyed in the reverse order, and thus less loss due toburning of the calcium takes place.

In employing the above alloys as a source of calcium when making calciumadditions to magnesium or magnesium base alloys, it is preferable tobring the desired quantity of the calcium rich alloy into contact withthe molten magnesium or magnesium base alloy. It is generally preferableto make the addition under the protection of a suitable flux such as theconventional potassium chloride-sodium chloride flux or while the moltenmagnesium is maintained under a protective gas such as natural gas,sulphur dioxide, hydrogen or the like.

In this manner, a predictable and definite amount of calcium can beadded to magnesium base alloys as desired without difliculty due toburning of the calcium, and at the same time a convenient source ofcalcium is furnished which may be stored over long periods of timewithout loss due to surface oxidation.

Other modes of applying the principl of my invemfiion may be employedinstead of the one explained, change being made as regarrds the methodherein disclosed, provided the step stated by any of the followingclaims or the equivalent of such stated step be employed.

I therefore particularly poinl: out and distinctly claim as myinvention:

1. The method of alloying calcium with magnesium which comprisesincorporating molten 10 CHARLES E. N ELSON.

